Understanding property in Python: Implementing a setter Without a getter

Explore how to create a `property` in Python that includes a `setter` without a `getter`, enhancing your understanding of property decorators in Python classes.
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Understanding property in Python: Implementing a setter Without a getter

When working with Python classes, you may find yourself needing to define properties for data encapsulation. The fancy terminology can be a bit overwhelming, but the core function is simple: properties allow controlled access to class attributes. One common question that arises is whether you can create a property that has a setter but not a getter. In this post, we’ll explore this curiosity and provide a solution to achieve just that.

The Problem

Consider the following example class that uses a property decorator. The class Dispatcher has a straightforward design where you can get and set a session:

[[See Video to Reveal this Text or Code Snippet]]

Although this implementation works perfectly, there are cases where you only want to set a value without exposing it through a getter, perhaps to prevent unintended access. This raises the question: Can we implement a property with only a setter in Python?

The Solution

Yes, you can! The simplest way to achieve a setter without a getter is to create a method for setting the value and then wrap it in a property declaration. Here’s how you can do it:

Implementation

Here’s the modified class:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

Private Attribute: The _session attribute remains private (denoted by the underscore). This is a common convention in Python, indicating that it should not be accessed directly from outside the class.

Setter Method: The _set_session method is defined to set the value of _session. This method will not be accessible as a standard method call from outside the class, but it will be invoked internally when setting the session property.

Property Declaration: The property() function is used only with the fset argument, linking it to the _set_session method. This means that while you can set the session attribute, you cannot retrieve it through a standard getter.

Testing the Implementation

Let’s run a quick test to see this in action:

[[See Video to Reveal this Text or Code Snippet]]

As shown in the test:

You can set the session value without any issues.

Conclusion

In summary, Python allows for great flexibility with properties, including the ability to create properties that only have setters. This technique can be particularly useful for ensuring that certain internal states are not publicly accessible. By using a setter method wrapped in the property() function, we can maintain control over how our class states are modeled and accessed.

If you ever find yourself in need of a setter without exposing a getter, remember this approach, and you’ll have yet another tool in your Python programming toolkit!